On Sun, Jul 15, 2018 at 12:12:44PM +0200, Greg Kroah-Hartman wrote: > On Sun, Jul 15, 2018 at 01:06:32PM +0300, Dmitry Torokhov wrote: > > On Sun, Jul 15, 2018 at 10:42 AM Marcus Folkesson > > <[email protected]> wrote: > > > > > > On Sat, Jul 14, 2018 at 08:51:09AM +0000, Dmitry Torokhov wrote: > > > > On Sat, Jul 14, 2018 at 10:09:20AM +0200, Marcus Folkesson wrote: > > > > > Hi Alexey, > > > > > > > > > > Good catch! > > > > > > > > > > On Fri, Jul 13, 2018 at 11:07:57PM +0300, Alexey Khoroshilov wrote: > > > > > > pxrc_probe() calls usb_get_dev(), but there is no usb_put_dev() > > > > > > anywhere in the driver. > > > > > > > > > > > > The patch adds one to error handling code and to pxrc_disconnect(). > > > > > > > > > > > > Found by Linux Driver Verification project (linuxtesting.org). > > > > > > > > > > > > Signed-off-by: Alexey Khoroshilov <[email protected]> > > > > > > > > > > Reviewed-by: Marcus Folkesson <[email protected]> > > > > > > > > Hmm, the biggest question however if we need to "take" the device, as I > > > > do not think interface can outlive the device, and whether we actually > > > > need to store it in pxrc, as we only need it during set up, as far as I > > > > can see. > > > > > > Yep, the device is only used during setup. > > > I interpret the comments for usb_get_dev() as you should take a > > > reference count on the device even if you only use the interface, but I > > > could be wrong. > > > > > > From usb_get_dev():: > > > > > > * usb_get_dev - increments the reference count of the usb device > > > structure > > > * @dev: the device being referenced > > > * > > > * Each live reference to a device should be refcounted. > > > * > > > * Drivers for USB interfaces should normally record such > > > references in > > > * their probe() methods, when they bind to an interface, and > > > release > > > * them by calling usb_put_dev(), in their disconnect() methods. > > > > Hmm, usb device is a parent of usb interface so our driver model rules > > ensure that usb device should not disappear while interface device is > > still there. Greg, is this comment still valid? > > Yes, that is true. But remember that interface devices can go away > while the parent is still present, so if you need the interface pointer, > you have to grab a reference on it.
But not in a simple interface driver, as we'll unbind the driver before destroying the interface... IOW we need to record the reference only if we are doing something unusual. Thanks. -- Dmitry
